This application claims the priority of German Patent Application Serial No. 199 06 023.1, filed Feb. 10, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates, in general, to a connector for a coaxial cable with smooth outer cable conductor, and more particularly to a connector of a type including a connector head having a recess for threaded engagement of a hollow screw which surrounds the cable.
The use of connectors for coaxial cables with a diameter of normally less than 10 mm and with smooth outer cable conductor in the form of either a braided metal foil or a braiding of numerous thin single wires is generally known. Normally, the inner cable conductor is soldered with the inner connector conductor retained in the connector head, whereas the outer cable conductor is folded back by a short piece at the end and clamped by the hollow screw inside the recess of the connector head.
Coaxial cables for commercial application, especially for transmitting greater power, typically have a massive, helically corrugated or annularly corrugated outer conductor to impart the cable with a certain flexibility, without encountering a deterioration of the electric properties. Connectors for these types of coaxial cables can be supplied from the factory completely pre-assembled and mounted to the end of the coaxial cable, without requiring a preceding dismantling thereof. Their use is in particular suitable in exposed sites of installation such as antenna masts or the like, because the installation can be executed in a time-saving manner and in a more secure fashion. An example of such a connector is described in German Pat. No. 43 43 229 C2.
Recently, coaxial cables for commercial application have been encountered which have a massive, smooth outer conductor and still exhibit sufficient flexibility. The use of conventional, pre-assembled connectors, as described above and employed for cables with corrugated outer conductor, is however unsuitable for coaxial cables with smooth outer conductor, because the installation is based on the principle of providing, i.a., a form-fitting engagement between components of the connector and the corrugated outer cable conductor.
It is thus an object of the present invention to provide an improved connector, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved connector which can be mounted pre-assembled onto a coaxial cable with a smooth outer cable conductor, without requiring a preceding dismantling thereof.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by providing a connector head having a ring surface for establishing a contact from inside with an outwardly deflected end zone of an outer cable conductor; a contact sleeve adapted to fit over the outer cable conductor and having a plurality of radially resilient segments terminating in beaded ends, wherein the contact sleeve, when not subject to a load, has an inner diameter which in the area of the beaded ends of the segments is smaller than a diameter of the outwardly deflected end zone of the outer cable conductor and in the remaining area is greater than the diameter of the outwardly deflected end zone of the outer cable conductor; and a hollow screw adapted to fit over the contact sleeve and formed with a thread for threaded engagement with the connector head, wherein the hollow screw, after traveling a clamping path, loads the segments of the contact sleeve in a direction of a clamping action so that the segments clamp the end zone of the outer cable conductor against the ring surface of the connector head.
A connector according to the present invention can be installed to one end of the coaxial cable, without preceding dismantling thereof because the novel and inventive design of the pre-assembled connector allows the installer to simply slip the connector over the prepared cable end until reaching a tactile resistance. Subsequently, the installer needs only to rotate the hollow screw into the connector head until a specified torque has been reached, indicating a sufficiently tight clamping action of the outer cable conductor. Yet, the installer has the option to completely unscrew the hollow screw from the connector head for dismantling the connector, should such action become necessary for any reason.
Thus, the connector according to the present invention for attachment to a coaxial cable with smooth outer conductor has the same advantages as a pre-assembled and mounted connector for a coaxial cable with corrugated outer conductor.
According to another feature of the present invention, the connector is provided with an indexing mechanism for subdividing the clamping path of the threaded clamping bush into first and second sections, with the first section corresponding to a pre-assembled state of the connector, and with the second segment corresponding to a complete assembly of the connector onto the cable end. The provision of such an indexing mechanism enables an installer to correctly preassemble and reattach the connector to the coaxial cable, if for some reason, the connector has been previously completely disassembled.
The indexing mechanism for subdividing the clamping path of the hollow screw may be implemented by providing an O ring which is received in an annular groove so positioned that the O ring engages a confronting end face of the connector head at the end of the first section and is moved conjointly with the hollow screw when the hollow screw travels along the second clamping path section. This configuration of the indexing mechanism is especially easy to implement and thus cost-efficient. In addition, the O ring may also provide a seal between the connector head and the hollow screw.
According to another feature of the present invention, the hollow screw has an axial end, which confronts the connector head, and includes a portion extending axially inwardly of the annular groove at a length, which is at least equal to a length of the second section of the clamping path, and being defined by an outer diameter which is smaller than an inner diameter of the recess of the connector head.
The installation can be facilitated when providing the hollow screw interiorly with a radially inwardly projecting shoulder which forms a stop for a ring collar of the contact sleeve and so limits a displacement of the contact sleeve in the pre-assembled state of the connector that a gap is defined between the ring surface of the connector head and the segments of the contact sleeve for insertion of the end zone of the outer cable conductor. The inwardly directed shoulder of the hollow screw may assume even a further purpose, namely to transmit the thrust of the hollow screw onto the contact sleeve. Suitably, the shoulder is then configured as continuous or interrupted ring shoulder having a connector-proximal end face which transmits the clamping force at the end of the second clamping path section onto confronting surfaces of the beaded ends of the segments of the contact sleeve.
The beaded ends of the segments of the contact sleeve may define ramp surfaces respectively formed on a peripheral conical surface area for interaction with the end zone of the outer cable conductor, whereby the conical surface area defines a cone angle which is so selected that the segments deflect radially outwards when an axial force applied by the end of the outer cable conductor upon the ramp surfaces of the beaded ends is exceeded.
As the connection between the cable and the connector should, in general, comply with very high mechanical and electrical standards, as far as resistance against separation and intermodulation freedom are concerned, at least one of the surfaces, which realizes the clamping action of the end zone of the outer cable conductor, has at least one bead for improving the clamping action and contact-making capability.